This reverts commit a55a5305982d996a4db88c2525299edc836ebccf.
The _opp_supported_by_regulators used by debug part, and that missed
in current backport. so revert this commit to avoid a unused warning.
Reported-by:Jon Medhurst (Tixy) <tixy@linaro.org>
Signed-off-by: Alex Shi <alex.shi@linaro.org>